Method for Manufacturing Ultra-High Molecular Weight Polypropylene

The present invention relates to a method for producing an ultra-high molecular weight polypropylene, and in particular, to a method for producing an ultra-high molecular weight polypropylene through molecular weight regulation according to an input ratio of titanium tetrachloride, alkyl aluminum, and an external electron donor in the preparation of the ultra-high molecular weight polypropylene, and an ultra-high molecular weight polypropylene produced thereby containing a trace amount of inorganic material through a catalyst residue removal process.

In general, polypropylene polymerization is performed by using magnesium chloride as a carrier, titanium chloride containing phthalate, di-ether, and succinate compounds as an internal electron donor as a main catalyst, alkyl aluminum as a co-catalyst, and a silicon compound containing an alkoxy group as a promoter, which is an external electron donor, and the polymerization is performed within a reactor such as slurry polymerization, bulk polymerization, or gas phase polymerization. At this time, hydrogen is used as a molecular weight regulator to regulate the molecular weight of the polymerized polypropylene, and all polypropylenes to be currently produced and supplied have Melt Index (MI) of 0.1 to 1,500 g/10 min under a load of 2.16 kg by the method suggested by ASTM D-1238.

The produced polypropylenes are applied to a variety of applications such as films, fibers, automobile interior and exterior materials, pipes, etc., and the melting point and density may be controlled by controlling MI or injecting comonomers according to the application.

Although these various applications are possible, the development of an ultra-high molecular weight polypropylene is required due to the development of processing technology and the need for materials suitable for discovering new uses, so as to have more improved mechanical properties and new applications, but there are limitations in a method for producing a polypropylene resin with a higher level of molecular weight only by a controlling method according to the injected amount of hydrogen.

In order to solve the problems described above, an object of the present invention is to provide an ultra-high molecular weight polypropylene that has a high molecular weight of 1,000,000 g/mol or greater and a high catalytic activity based on a viscosity average molecular weight through changes in polymerization temperature and pressure by controlling selection of a main catalyst and a ratio of main catalysts, co-catalysts, promoters, etc., in a method for producing an ultra-high molecular weight polypropylene.

Another object of the present invention is to provide an ultra-high molecular weight polypropylene that has a lower level of inorganic content and an average particle diameter of 400 μm or less in order to improve the performance of a capacitor film and a secondary battery separator in a method for producing an ultra-high molecular weight polypropylene.

To achieve the above objectives, the present invention includes a method for producing an ultra-high molecular weight polypropylene characterized by controlling a ratio of a main catalyst (a) which is a titanium compound, a co-catalyst (b) which is an alkyl aluminum compound, and a promoter (c) which is a silicon compound, polymerization temperature, and polymerization pressure without adding hydrogen which is a molecular weight regulator to produce an ultra-high molecular weight polypropylene of 1,000,000 g/mol or greater.

Here, Al in the co-catalyst, which is the alkyl aluminum compound, may be included in 10 to 500 moles with respect to 1 mole of Ti in the main catalyst, which is the titanium compound.

Here, Si in the promoter, which is the silicon compound, may be included in 1 to 40 moles with respect to 1 mole of Ti in the main catalyst, which is the titanium compound.

Here, the polymerization temperature may be 30 to 90° C.

Here, the polymerization pressure may be 1 to 40 bar.

Here, the method for producing the ultra-high molecular weight polypropylene may further include mixing a polar organic solvent (x) with the produced ultra-high molecular weight polypropylene, and separating, purifying and drying the mixture using distilled water (y) or filtered water (y′), in order to remove catalyst residues in the produced ultra-high molecular weight polypropylene.

Here, the polar organic solvent (x) may be any one or more compounds selected from a group consisting of a compound of Chemical Formula (4) below and a compound of Chemical Formula (5) below:

(In Chemical Formula (4) above, R may be a linear or branched alkyl group having 1 to 12 carbon atoms, and the Chemical Formula (4) may be any one or more compounds selected from a group consisting of methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, octanol, nonanol, decanol, undecanol, dodecanol, and branched alkyl groups such as isopropanol, isobutanol, and isopentanol.

In Chemical Formula (5) above, R1 and R2 may be linear alkyl groups having 1 to 6 carbon atoms, and the Chemical Formula (5) may be any one or more compounds selected from a group consisting of methanediol, ethanediol, propanediol, butanediol, pentanediol, hexanediol, heptanediol, octanediol, nonanediol, decanediol, undecanediol, and dodecanediol.)

Here, 10 to 1000 parts by weight of the polar organic solvent (x) may be mixed with respect to 100 parts by weight of the produced ultra-high molecular weight polypropylene.

Here, 100 to 3000 parts by weight of the distilled water (y) or filtered water (y′) may be used with respect to 100 parts by weight of the polar organic solvent (x).

In another general aspect, to achieve the above objectives, the present invention further describes an ultra-high molecular weight polypropylene produced according to the method for producing an ultra-high molecular weight polypropylene and having a viscosity average molecular weight of 1,000,000 g/mol or greater.

Here, the viscosity average molecular weight of the ultra-high molecular weight polypropylene may be 1,000,000 to 4,000,000 g/mol.

Here, the ultra-high molecular weight polypropylene may have an inorganic content of 30 ppm or less.

Here, the ultra-high molecular weight polypropylene may have a particle diameter of 400 μm or less.

According to the method for producing the ultra-high molecular weight polypropylene of the present invention as described above, there is the effect that the molecular weight regulation for producing an ultra-high molecular weight propylene can be achieved with an input ratio of a main catalyst, a co-catalyst and a promoter even if hydrogen used as a molecular weight regulator in general polymerization conditions is not added.

In addition, the ultra-high molecular weight polypropylene produced according to the present invention contains a lower level of inorganic materials than polypropylene resins generally produced through a catalyst residue removal process to have physical properties suitable for secondary battery separators and uses requiring insulation.

In addition, according to the method for producing the ultra-high molecular weight polypropylene of the present invention, it is possible to produce an ultra-high molecular weight polypropylene separator having excellent performance and a heterogeneous separator of ultra-high molecular weight polyethylene and ultra-high molecular weight polypropylene by improving the kneading property and melting rate with the ultra-high molecular weight polyethylene used in secondary battery separators through particle diameter control.

The terms used herein are intended to describe embodiments and are not intended to limit the present invention. In the present specification, a singular form also includes a plural form unless specifically stated in the text. As used in the specification, “comprises” and/or “made of” do not preclude the presence or addition of one or more other components, steps, operations and/or elements mentioned.

Unless otherwise defined, all terms used in the present specification may be used in a meaning commonly understood by those skilled in the art to which the present invention pertains. In addition, terms defined in commonly used dictionaries are not ideally or excessively interpreted unless clearly and specifically defined.

The present inventors have completed the present invention by confirming that an ultra-high molecular weight polypropylene having a viscosity average molecular weight of 1,000,000 g/mol or greater according to the present invention as follows. Meanwhile, the term “ultra-high molecular weight” as used herein means a viscosity average molecular weight of 1,000,000 g/mol or greater.

The present inventors have devised the following invention as a result of research to solve the above problems. In the present specification, there is described a method for producing an ultra-high molecular weight polypropylene characterized by controlling a ratio of a main catalyst (a) which is a titanium compound, a co-catalyst (b) which is an alkyl aluminum compound, and a promoter (c) which is a silicon compound, polymerization temperature, and polymerization pressure without adding hydrogen which is a molecular weight regulator to produce an ultra-high molecular weight polypropylene of 1,000,000 g/mol or greater.

In addition, in order to achieve the above-mentioned object, the present invention provides a method for producing an ultra-high molecular weight polypropylene including performing a polymerization reaction by using a main catalyst having high stereoregularity and adding a content of a co-catalyst and an optimal content of an external electron donor capable of initiating the catalyst and minimizing the separation of a molecular main chain.

More specifically, the present invention provides a method for molecular weight regulation of an ultra-high molecular weight polypropylene according to an input ratio of the main catalyst, the co-catalyst and the promoter.

The method for producing the ultra-high molecular weight polypropylene of the present invention is as follows, for each step process of:

Here, step (x) is preferably performed under a nitrogen atmosphere. That is, step (x) is preferably performed in the presence of inert gas.

In the method for producing the ultra-high molecular weight polypropylene of the present invention, the hydrocarbon solvent including 1 to 20 carbon atoms in step (x) may include at least any one selected from the group consisting of aliphatic hydrocarbon solvents such as pentane, hexane, cyclohexane, methyl cyclohexane, heptane, octane, decane, undecane, dodecane, tridecane or tetradecane; aromatic hydrocarbon solvents such as benzene, toluene, xylene or ethyl benzene; and halogenated hydrocarbon solvents such as dichloropropane, dichloroethylene, trichloroethylene, carbon tetrachloride or chlorobenzene. In addition, the method may also be performed by gas phase polymerization or bulk polymerization under high pressure of propylene without hydrocarbons.

In the method for producing the ultra-high molecular weight polypropylene of the present invention, representative examples of the co-catalyst b in step (x) may include at least any one compound selected from a group consisting of triethylaluminum, trimethylaluminum, triisobutylaluminum, trioctylaluminum, diethylaluminum chloride, diethylaluminum bromide, diethylaluminum iodide, diethylaluminum fluoride, ethylaluminum dichloride, dimethylaluminum chloride, metalaluminum dichloride, and ethylaluminum sesquichloride.

In step (x), the co-catalyst (b) is preferably added in an amount of 5 to 500 moles per 1 mole of the main catalyst (a), more specifically added in an amount of 10 to 500 moles, and most preferably added in an amount of 100 to 500 moles, but is not limited thereto. More specifically, it is preferable that Al in the co-catalyst (b), which is an alkyl aluminum compound, is included in 5 to 500 moles with respect to 1 mole of Ti in the main catalyst (a), which is a titanium compound. For example, if Al in the co-catalyst (b), which is the alkyl aluminum compound, is less than 5 moles with respect to 1 mole of Ti in the main catalyst (a), which is the titanium compound, there may be a problem in that the polymerization reaction does not sufficiently occur. On the contrary, if Al of the co-catalyst (b), which is the alkyl aluminum compound, is more than 500 moles with respect to 1 mole of Ti in the main catalyst (a), which is the titanium compound, even if the polymerization reaction occurs, the ultra-high molecular weight polypropylene with a viscosity average molecular weight of 1,000,000 g/mol or greater may be not sufficiently produced.

In addition, in step (x), the main catalyst (a) is a Ziegler-Natta-based titanium chloride catalyst containing a silicon compound containing phthalate, di-ether, and succinate as an internal electron donor, and magnesium chloride as a carrier, and suitably titanium trichloride or titanium tetrachloride, and a catalyst that provides high stereoregularity depending on a type of internal electron donor is more preferable, and generally, commercially available catalysts may be used.

In addition, in step (x), the promoter (c) may be used with any one or more compounds selected from the group consisting of a compound of the following Chemical Formula (1), a compound of the following Chemical Formula (2), and a compound of the following Chemical Formula (3).

In Chemical Formulas (1) to (3),

Ra, R7, R8 and R9 are each independently an alkyl group, cycloalkyl group, aryl group, allyl group or vinyl group having 1 to 12 carbon atoms, Rb is an alkyl group or aryl group having 1 to 6 carbon atoms, R is an alkyl group, cycloalkyl group, aryl group, or allyl group having 1 to 12 carbon atoms, or —ORc, in which Rc is an alkyl group or aryl group having 1 to 6 carbon atoms, and n is an integer of 0 to 6.

Specifically, representative examples of the compound of Chemical Formula (1) may include any one or more compounds selected from the group consisting of cyclohexylmethyldimethoxy silane (CMCD), cyclohexyl-n-propyldimethoxy silane (CPDM), cyclohexyl-1-propyldimethoxy silane (CIPDM), cyclohexyl-n-butyldimethoxy silane (CBDM), cyclohexyl-1-butyldimethoxy silane (CIBDM), cyclohexyl-n-hexyldimethoxy silane (CHDM), cyclohexyl-n-octyldimethoxy silane (CODM), cyclohexyl-n-decyldimethoxy silane (CDeDM), dimethyldimethoxy silane, dimethyldiethoxy silane, dicyclopentyldimethoxy silane, diisopropyldimethoxy silane, dicyclopentyldimethoxy silane, methylphenyldimethoxy silane, diphenyldiethoxy silane, methyltrimethoxy silane, ethyltrimethoxy silane, vinyltrimethoxy silane, phenyltrimethoxy silane, methyltriethoxy silane, ethyltriethoxy silane, vinyltriethoxy silane, phenyltriethoxy silane, butyltriethoxy silane, ethyltriisopropoxy silane, vinyltributoxy silane, and methyltriaryloxy silane. Preferably, representative examples of the compound of Chemical Formula (1) may include any one or more compounds selected from the group consisting of dimethyldimethoxy silane, dimethyldiethoxy silane, dicyclopentyldimethoxy silane, cyclohexylmethyldimethoxy silane, diisopropyldimethoxy silane, dicyclopentyldimethoxy silane, methylphenyldimethoxy silane, diphenyldiethoxy silane, methyltrimethoxy silane, ethyltrimethoxy silane, vinyltrimethoxy silane, phenyltrimethoxy silane, methyltriethoxy silane, ethyltriethoxy silane, vinyltrimethoxy silane, phenyltriethoxy silane, butyltriethoxy silane, ethyltriisopropoxy silane, vinyltributoxy silane, and methyltriaryloxy silane.

Representative examples of the compound of Chemical Formula (2) may include any one or more compounds selected from the group consisting of 1,1,3,3-tetramethoxy-1,3-dimethyl-1,3-disilapropane (TMDMDP), 1,1,3,3-tetramethoxy-1-methyl-3-hexyl-1,3-disilapropane (TMMHDP), 1,1,3,3-tetramethoxy-1,3-di-n-hexyl-1,3-disilapropane (TMDHDP), 1,1,3,3-tetramethoxy-1-methyl-3-cyclohexyl-1,3-disilapropane (TMMCDP), 1,1,3,3-tetramethoxy-1,3-dicyclohexyl-1,3-disilapropane (TMDCDP), 1,1,8,8-tetramethoxy-1,8-dicyclohexyl-1,8-disilaoctane (TMDCDO), and 1,1,3,3-tetramethoxy-1,3-dimethyldisiloxane (TMDMDS).

Representative examples of the compound of Chemical Formula (3) may include any one or more compounds selected from the group consisting of methyl (trimethylsilylmethyl)dimethoxysilane (MTDM), n-propyl (trimethylsilylmethyl)dimethoxysilane (PTDM), i-propyl (trimethylsilylmethyl)dimethoxysilane (IPTDM), n-butyl (trimethylsilylmethyl)dimethoxysilane (BTDM), i-butyl (trimethylsilylmethyl)dimethoxysilane (IBTDM), n-pentyl (trimethylsilylmethyl)dimethoxysilane (PnTDM), n-hexyl (trimethylsilylmethyl)dimethoxy silane (HTDM), cyclopentyl (trimethylsilylmethyl)dimethoxysilane (CpTDM), and cyclohexyl (trimethylsilyl methyl)dimethoxysilane (CTDM).

In step (x), the promoter (c) is preferably added in an amount of 1 to 40 moles per 1 mol of the main catalyst (a), but is not limited thereto. More specifically, it is preferable that Si in the promoter, which is a silicon compound, is included in an amount of 1 to 40 moles with respect to 1 mole of Ti in the main catalyst, which is a titanium compound. For example, if Si in the promoter, which is the silicon compound, is less than 1 mole with respect to 1 mole of Ti in the main catalyst (a), which is the titanium compound, there may be a problem in that the polymerization reaction does not sufficiently occur. On the contrary, if Si in the promoter, which is the silicon compound, is more than 40 moles with respect to 1 mole of Ti in the main catalyst (a), which is the titanium compound, even if the polymerization reaction occurs, there may be a problem in that the ultra-high molecular weight polypropylene with a viscosity average molecular weight of 1,000,000 g/mol or greater may be not sufficiently obtained.

Meanwhile, in step (y), the polymerization temperature at which the polymerization reaction is performed by adding a propylene d to the mixed solution is preferably within the range of 30 to 90° C., but is not limited thereto. For example, if the polymerization temperature at which the polymerization reaction is performed is less than 30° C., there may be a problem in that the polymerization reaction does not sufficiently occur. Conversely, if the polymerization temperature at which the polymerization reaction is performed is more than 90° C., even if the polymerization reaction is performed, there may be a problem in that the ultra-high molecular weight polypropylene with a viscosity average molecular weight of 1,000,000 g/mol or greater may be not sufficiently obtained.

In addition, in step (y), the polymerization pressure at which the polymerization reaction is performed by adding the propylene (d) to the mixed solution is preferably within the range of 1 to 40 bar, but is not limited thereto. For example, if the polymerization pressure at which the polymerization reaction is performed is less than 1 bar, there may be a problem in that the polymerization reaction does not sufficiently occur. Conversely, if the polymerization pressure at which the polymerization reaction is performed is more than 40 bar, even if the polymerization reaction is performed, there may be a problem in that the ultra-high molecular weight polypropylene with a viscosity average molecular weight of 1,000,000 g/mol or greater may be not sufficiently obtained.

Meanwhile, the polymerization reaction performed in step (y) may be performed in liquid phase, slurry phase, bulk phase, or gas phase polymerization, but is not limited thereto.

In addition, in order to achieve the above-mentioned object, the present invention provides a catalyst residue removal process along with the production of the ultra-high molecular weight polypropylene, and provides a method for removing inorganic materials such as magnesium, titanium, aluminum, and silicon that have been used as a catalyst in the polymerization process.